The keyboard maps are generated from appropriate .map files by running
loadkeys --mktable. However, there are two reasons to provide shipped
versions and use those by default

1) Not everybody has loadkeys installed.
2) As pointed out by Andries Brouwer, if changes to the tables occur in
   the kernel tree, that may require a new/recompiled version of loadkeys,
   so that the version of loadkeys required for the kernel build is
   often ahead of the installed base.

For these reasons, we provide shipped versions of the generated files and
use them unless the user explicitly asks for regenerating by uncommenting
the appropriate line in the Makefile.